Currently there are tens of thousands of depleted oil and natural gas wells around the world, which collectively possess significant amounts of petroleum resources that cannot currently be extracted using conventional extraction techniques.
For example, in a typical oil well, only about 30% of the underground oil is recovered during initial drilling (“primary recovery”). An additional approximately 20% of the original oil may be accessed by “secondary recovery” techniques such as water flooding. In recent years, “tertiary recovery” (also known as “Enhanced Oil Recovery” or EOR) techniques have been developed to recover additional oil from depleted wells. Such tertiary recovery techniques include thermal recovery, chemical injection, and gas injection. Using current methods, these tertiary techniques allow for an additional 20% or more of the original oil to be recovered.
Gas injection is one of the most common EOR techniques. In particular, carbon dioxide (CO2) injection into depleted oil wells has received considerable attention owing to its ability to mix with crude oil. Since crude oil is miscible with CO2 at moderate pressures and temperatures, injection of CO2 renders the oil substantially less viscous and more amenable to recovery.
Despite the potential advantages of CO2 in enhanced oil recovery, its use has been hampered by several factors. For instance, in order for the enhanced recovery process to be economically viable, the CO2 gas must be available in copious supplies at reasonable cost at the site of the oil well. Alternatively, CO2 can be produced from industrial applications such as natural gas processing, fertilizer, ethanol and hydrogen plants where naturally occurring CO2 reservoirs are not available. The CO2 must then be transported over large distances via pipelines and injected at the well site. Unfortunately, such CO2 pipelines are difficult and costly to construct. Additionally, many oil sites are out of reach from such natural and industrial sources of CO2.
Additionally, as a result of widespread concern over global warming, proposals are being considered to create taxes on CO2 emissions, with typical figures in the range of $50 per tonne of CO2 released into the atmosphere. However, most electric power plants, which burn coal or natural gas to generate electricity, produce large quantities of CO2 waste product. Using present technologies, it is often not economically feasible to utilize the CO2 from such power plants for oil recovery because they are not within close reach of oil fields. Thus, the cost of sequestering CO2 in the ground is often not economically feasible.
In addition to CO2, another gas that can potentially be used for enhanced oil recovery is hydrogen (H2). Hydrogen gas has received considerably less attention than CO2, however. Hydrogen, although somewhat soluble with oil, is far less so than CO2. Large quantities of hydrogen are believed to be necessary for pressurization and long residence times are believe necessary for in-situ hydrogenation. Traditionally, hydrogen has been costly to produce and its use has not been justified from an economic standpoint.
As recognized by the present inventors and described in related patent applications, what is needed is a portable and modular system and apparatus that may be taken wherever a candidate oil field may be, for extracting oil/petroleum from the ground or from oil wells, such as “depleted” oil wells and for generating electricity without harmful greenhouse gas emissions.
However, as recognized by the present inventors, what are also needed are control methods and control systems for controlling the portable/modular oil extracting/power generating apparatus based on such factors as subsurface data, and market prices of crude oil and electricity. What is needed is an automatic control system and method for automatically controlling the oil extracting apparatus with minimum human supervision.
Therefore, it would be an advancement in the state of the art to provide a control system and a control method for a portable/modular apparatus that automatically controls the apparatus to generate carbon dioxide for enhanced oil recovery and to generate electricity from hydrogen.
It is against this background that various embodiments of the present invention were developed.